Method for cooling metal webs

ABSTRACT

The disclosure relates to a method and to an apparatus for cooling continuously cast webs of metal. Several coolant jets are produced continuously and at least two jets are projected to a hotter, slowly cooling zone of the surface of the webs.

United States Patent [191 Wagener et al.

[451 Aug. 21, 1973 METHOD FOR COOLING METAL WEBS [75] Inventors: Elrnnr Wagener, Neukirchen-Vluyn,

Germany; Frantisek Jansch, U Pergamenky, Czechoslovakia [73] Assignee: DEMAG Aktiengesellschaft,

Duisburg, Germany 221 Filed: o.27,1971

211 Appl. No.: 192,885

[30] Foreign Application Priority Data Nov. 3, 1970 Germany P 20 53 947.3

[52] US. Cl 148/13, 134/15, 148/3, 148/134, 148/143, 164/89 [51] Int. Cl. C22f 1/00 [58] Field of Search 148/3, 13, 134, 143;

[56] References Cited UNITED STATES PATENTS 3,698,700 10/1972 Ziehm et a1 148/13 Primary Exqg rt iner Richard Dean Att0meyHubeit T. Mandeville, Michael A. Comman et al.

[ 5 7 ABSTRACT The disclosure relates to a method and to an apparatus for cooling continuously cast webs of metal. Several coolant jets are produced continuously and at least two jets are projected to a hotter, slowly cooling zone of the surface of the webs.

7 Claims, 10 Drawing Figures METHOD FOR COOLING METAL WEBS BACKGROUND OF THE INVENTION An important problem in extruding metals is the cooling process. Ordinarily the molten metal is directed through a die having an aperture determinative of the cross-section of the web or continuous casting. This socalled continuous casting die is cooled at its walls so that the heat of the molten metal is transferred to its shell walls and discharged through the cooling water circulating in the continuous shell. However, only a relatively small portion of the amount of heat present in the molten metal can be removed in the continuous shell. The amount of heat removed only suffices to form an outer solidified layer of the web. Particularly with the casting of steel whose low heat conductivity is further reduced due to alloy components, it has been impossible to remove adequately the heat in sufficient amount to allow high speed casting operations. Thus Webs cast from metal with a high heat content are subjected to a second cooling process which takes place more or less in the ambient atmostphere outside the continuous die shell. The coolant used typically consists of water and optional appropriate additives to increase the heat absorption capacity and accommodate an elevation of the evaporation point of the coolant.

According to a method of prior art, water is sprayed from atomizer nozzle in selective zones upon the surface of the continuous casting. The coolant impact areas are approximately elliptical in cross-sectional shape. The cross-sectional shape of the continuous casting, which is rectangular in most cases, requires a particular cooling behavior. Internal core sections of the rectangular-web located about its center, of course, cool more slowly than exterior peripheral surfaces. In order to reinforce the cooling effect, it is known to arrange coolant impact areas in rows over the width of the web so closely together that lateral overlappings of the atomizing jets occur. Overlapping of the atomizing jets causes a reduction of the jet energy. Consequently, it is necessary to find for each of the zones to be impacted, the proper positioning and spacing of the nozzles in relation to the surface of the continuous casting to develop the largest possible effect of the coolant. In order to influence further the cooling intensity, other measures are available, including changing the angle of projection of the coolant, changing the characteristic of the projection of the coolant, and changing the shape of the impacted surface so sprayed.

It has been discovered that a plurality of metals, among them steel, can be cooled more rapidly with more powerful spray cooling conditions without causing fissures in the material. Nevertheless, the cooling intensity must be adjusted to the most important values of the extrusion system and to the material to be cast.

According to prior art the cooling intensity could be amplified only by increasing the pressure of the coolant jet and/or by enlarging the cross-section of the jet. However, a reciprocal influencing of the atomized jets causes losses of kinetic energy of about ten to twenty per cent. Moreover, the increase of pressure as a factor for boosting the cooling intensity may possibly lead to undesirable side effects at the nozzles. The boost in pressure thus remains only measure within a number of factors influencing the effect of the atomized jet. The thickness of the atomized jet is also restricted by the gap distance of the supporting members, such as sup porting rollers.

An effective, zonewise amplified cooling of a cast metal web heretofore has presented an unsolved problem. The present invention is directed to a solution of the problem i.e., to improving the cooling effect according to the cooling behavior of a continuous castings of predetermined crosssections in order that the casting process may be accomplished faster thereby increasing the yield of extruded metal in a given period.

SUMMARY OF THE PRESENT INVENTION According to the present invention, a new method is proposed wherein coolant is delivered at one or several discharge apertures in a jet or jets which cover the entire surface of the web, which travels in an approximately uniformly thick layer. Advantageously, at least two jets of different planes are intersected prior to their impact of which at least one plane deviates from a per pendicular plane through the web surface zone being cooled. Several advantages are connected with the generation of a coolant stream over the full width of the web. Each zone of the web surface passes through a cooling zone, within which the cooling effect is synchronized with the amount of heat yielded locally. The formation of the cooling jet thus can be accomplished at different longitudinal points of the continuous casting for a differential cooling effect. The intersecting of the jets on the other hand, causes a substantial increase of the width of the flat coolant jet pattern even at higher pressures. The kinetic energy can be utilized better than heretofore for the building up of the spray characteristic, that is for the distribution of the pressure over the width of the casting surface moving below the cooling jet. One particular effect is obtained by intersecting two jet planes (or fans) by converting the kinetic energy into pressure energy thus leading to a broadening of the relativelynarrow fan thickness of the cooling jets. The high kinetic energy ahead of the point of intersection, after conversion into pressure energy beyond the point of intersection, leads to an increase of the volume of the jet.

It is particularly advantageous to merge three flat fan jets approximately in a point of intersection proximal to the surface of the casting. The coolant used upon the surface strip of the web to be cooled, after the point of intersection, expands the prismatic volume of the jet to a very large extent. When the intersection is located relatively close to the web surface, the confinement of the coolant into particularly narrow gaps may be effected. Such narrow gap may be present as a result of the required web supporting means, such as supporting rollers. Therefore, the proposed cooling method may improve the available cooling effect by appropriate limitation of the impact surfaces available as dictated by the peculiarity of mechanical guidance means.

Expediently the web or casting is surroundedby fan jets which substantially extend transversely to the longitudinal direction of movement of the casting. That way the amount of heat to be removed remains constant per longitudinal web increment.

An especially uniform cooling over the width of the web takes place in particular when the coolant is so processed that the jet planes produce a generally stripeshaped to oblong oval pattern of projected spray on the moval of heat with the new patterns. As the separation of web and the point of intersection increases, the distribution of the coolant spreads to a progressively larger surface than the narrow stripe-shaped projection surface obtained by a close spacing of the intersection point to the web.

The intensity of the cooling can be regulated advantageously by jets of different jet fans, whereby they are directed against the surface of the csating from different distances.

It also is possible for the angles of the jet planes to be modified in relation to each other and/or to the surface of the web or casting, commensurate with the corresponding cooling intensity. The corresponding angle setting is a measure for increasing or decreasing the width of the cooling stripe on the web surface. Finally, by changing the quantity of the output of the jets, the coolant may be directed in individual planes in desired directions. This offers at the same time, the possibility of further controlling the cooling performance per unit of web surface.

A particularly advantageous apparatus for practicing the method of the invention, includes a multiple nozzle arrangement with the central axis of each issued jet fan disposed in separate planes. Each nozzle is connected to a supply conduit for coolants and may be fixed at a setting which is angularly adjustable in relation to the other nozzles and the issuing jet sprays. It is advantageous to provide a single nozzle with several discharge apertreus for each jet fan.

Each nozzle is pivoted by itself for the desired angular adjustment and it is pivoted to arrange the abovedescribed intersection. The jet stream characteristics located ahead of the point of intersection thereby do not change at a renewed angle adjustment, providing pressures and discharge apertures remain unmodified.

The apparatus now may be constructed with all the nozzles of all the jet sprays accommodated in a unitary housing. The nozzles thus are adjustable in rows.

According to an additional feature of the invention the nozzles for each cooling stripe are adjustable in the housing in distance and angularity, in relation to the casting surface. Therefore, the entire housing may be adjustable in distance and angularly.

DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of a moving casting web supported by rollers and being cooled with three intersecting jet fans;

FIG. 2 illustrates a single jet fan; FIG. 3 shows the impact pattern of the jet fan of FIG.

FIG. 4 is a schematic diagram of the distribution of the quantities of water across the width of the web;

FIG. 5 illustrates two intersecting jet fans;

FIG. 6 illustrates the projection planes of separate jet fans depicted without the effects of their intersection;

FIG. 7 illustrates another embodiment with three intersecting jets;

FIG. 8 shows the impact pattern on the cast web produced according to the apparatus of FIG. 7;

FIG. 9 shows a variation of the nozzle positions of the embodiment according to FIG. 7, and

FIG. 10 is a schematic diagram of the distribution of the amounts of water produced according to the apparatus'of FIG. 1 and to FIG. 9.

DESCRIPTION OF PREFERRED EMBODIMENT The cooling method of the invention is applied to a slab casting or web 1 of steel, (FIG.1). It should be understood that the applicability of the invention is not particularly limited to wide webs. Billet webs also may be cooled just as easily; thus neither the thickness nor the width of the web are critical limitations over the utility of the invention. The advantages of the invention may be derived in cooling castings with a large ratio of cross-section width to thickness, such as slabs or panels.

The cross-section 2 of the continuous casting 1 is generally rectangular. The steel is still molten, pasty, and of a higher temperature than the marginal ranges in the central cross-section area 3. The marginal ranges have chilled into a shell 4 which is increasingly hardened on the basis of the outer cooling, which is effected by the amount and spacing of molten core material from the continuous hardening shell. The cooling also is a function of the basic structure of an extrusion system. For the cooling, the parameters including shape of cross-section, dimensions, material-dependent heat conductivity, and casting speed are of essential importance. Moreover, external influences such as sharp bending of the web, or the pressing effect of the elements for guiding the casting must be taken into consideration. With the latter, overstress may occur on a metal web not sufficiently cooled, causing fissures on the inside or outside of the web.

Spraying cooling water at the outer surface of the continuous shell 4 is used for a rapid increase of the thickness of the same. Regions at larger distances from the continuous shell, i.e., the central core, of the casting ought to be so chilled at a rate that the materialdependent cooling curve is unifonn at all points of the cross-section of the web 2. In all areas of the length of the casting or web the method according to the invention may be adjusted with particular facility to local conditions. Thereby, in accordance with the invention, a cooling intensity is provided over the width 5 of the casting web 1, which intensity is proportional to the quantities of heat to be removed per unit of time and per volume of the web.

A cooling zone 8 is defined between two guiding rolls 6 and 7. In the direction of movement of the web the coolingzone 8 is limited by the guide rolls which either pump or aspirate the cooling water ahead ofthem. Pipes l0, constantly supplying coolant, for example cooling water of controlled temperature and purity, extend above the web surface 9 and/or the rolls 6 and 7. The pipes 10 may be fastened in an expedient manner (e.g., by clamps) to parts of the extrusion system (not shown). The fastening may be such that the spacing of the pipes 10 in relation to the surface of the casting web 9 is variable. For small amounts of coolant a single pipe 10 will suffice, as shown in the drawing. Nozzle bodies ll, 12 and 13 are fastened to the pipe 10. A plurality of discharge openings of round or oblong shape are formed in said bodies and, as shown, nozzle body ll, l2, 13, generates a spray fan 14,15,16. The lateral edges 17 of each of the fans are generally parallel or slightly divergent. Approximately equally thick jet sprays or fans l4, l5, 16 are established by the nozzle openings to stabilize the flow of coolant in each of the nozzle bodies ll, 12, 13 and to stabilize correspondingly the pressures of the coolant and/or corresponding flow rates in each nozzle. Theoretically the jet spray fans impact with their central planes 18 transverse to the direction of movement of the web surface 9. In case of particularly narrow webs, several jet fans also may be placed parallel to the direction of movement of the web. The distribution of the amount of water within the length of the jet spray (in longitudinal direction of the web) is then maintained almost constant.

In each of the illustrated embodiments of FIGS. 5, 7, and 9, the fan jets 14, and 16 meet and intersect at intersection 19. Before the intersection 19, the jet fans 14, 15, 16 are completely separated, but beyond the intersection, they emanate as a joint, unitary spray. Thus, the web may be covered uniformly with coolant over a considerably wide surface. A single fan jet 15, as shown in FIG. 2, produces only a narrow impact surface pattern 20, although it is possible thereby, according to FIG. 3, to achieve a stripe-shaped impact surface pattern extending over the entire width 5 of the web. The individual fan jet 15 establishes over the width 5 a weighted coolant distribution, as shown in FIG. 4. Thus, the quantity of water is greatest in the center 21 of the web, commensurate with the large quantity of heat to be removed therefrom and pursuant to the invention.

With two intersecting jet fans l4, 16 (FIG. 5), the distribution or pattern of the coolant on the surface of the web 9 is determined by the distribution of forces in the individual jets. If jet spray fan 14 is preponderant, the coolant is urged in the direction of the roller 7. With the jet spray fan 16 acting with greater force, the gap area 22 proximate the roller 6 will be favored. The illustration of spray impingement in FIG. 6 represents a momentarily prevailing condition of coolant distribution which, of course, is variable periodically by pressure fluctuations. It is particularly advantageous to employ alternating pressure variations in the jet sprays l4 and 16, when only two jets are used to create a large cooling zone 8, to work on a large portion of web surface 9.

The intersecting of several fans 14 and 16 also is advantageous to accommodate variations in spacing and diameters of pairs of supporting rollers 6 and 7 over the length of the course of the casting. More narrow support roller gaps may be filled more easily with coolant. Desirably, the coolant produces as large a cooling zone as possible, which zone may be composed in part of the casting surface 9 between rollers and the facing circumferential surfaces of the rollers themselves.

A considerably increased distribution of cooling effact for the coolant, in comparison with the two jet method, is shown in FIG. 7, which in assition is shown in perspective in FIG. 1. Three fans 14, 15 and 16 are directed at the intersection 19. A particularly favorable spacing is selected between intersection l9 and casting surface 9, which corresponds to approximately half the diameter of the supporting roller. The resultant coolant spray 23 impacting upon the casting surface 9 establishes a cooling zone 8 of the width 20 which is markedly enlarged in FIG. 8. The coolant of jet 23 possesses a high specific density.

The resultant coolant jet spray 23 may consist not only of the three spray fans 14, 15 and 16, but may also be generated from a plurality of fans contacting at the intersection l9, mixing with each other and/or deflecting therefrom. When three independent jet fans 14, 15 and 16 are generated, the characteristics and the influences of the individual layer jets on the resultant jet 23 may be varied, as shown in FIG. 9. In addition to increased or decreased pressure, variations may be developed by the spacings of the nozzle bodies 11 and 13 at different distances from the casting than the spacing of the symmetrically disposed nozzle body 12. The spraying width 20 of the jet fan 15 is greater according to FIG. 10 (diagram for the distribution of the water quantity) in the center area of the casting width 5 and it, therefore, produces a hump 24 in the diagram. Moreover, as in FIG. 4 a parabolic distribution of the amount of water 25 across casting width 5 is presupposed as a matter of principle, in order to take into account the lower cooling requirements at the marginal edges of the casting web 1.

The nozzle bodies l1, l2 and 13 are disposed in special housings 26 (FIG. 1), which may be universally, angularly oriented with respect to the web and pipes 27. Transport of the coolant from the main pipes 10 is effected through the pipes 27, as shown. The nozzle bodies 11, 12 and 13 also may be individually angularly adjustable with the housings 26, themselves. The pivotability and adjustability of the individual nozzle bodies l1, l2, 13 and/or of the housings 26 is provided for the adjustment of the spray planes in relation to the casting surface and to one another for controlling the distribution of water across the web.

We claim:

1. A method for chilling heated, travelling metal webs, comprising a. continuously generating at least two coolant fan jet streams;

b. projecting the centers of said streams toward hotter, more slowly cooling, zones of the web;

0. said coolant streams being developed in plural discharge apertures and extending across the full width of said web; i

d. said coolant flowing in approximately uniformly thick spray fan cross section and having a greater volume of coolant at its central portions than its edge portions;

e. intersecting said fans prior to their impingement against the web surface;

f. at least one of said fans disposed in a plane disposed at an angle other than with the web surface.

2. A method according to claim 1, further characterized in that a. three fan jet streams are merged approximately at a point of intersection adjacent to the web surface.

3. A method according to claim 2, further characterized in that a. the fan jet sprays extend transversely of the direction of movement of the web. 4. A method according to claim 3, further characterized in that a. the jet fans produce cross-sectional projection patterns ranging from generally stripe-shaped to oblong oval shaped. 5. A method according to claim 4, further characterized in that a. sprays of different fans are directed upon the surface of the web from different elevations thereabove. 6. A method according to claim 5, further characterized in that 7 8 a. the angles of the jet fans are adjusted in predeter- 7. A method according to claim 6, further charactermined relation to each other and/or to the surface ized in that of the web to distribute coolant in suitably a. the quantitative output of the jets in individual fans weighted quantities commensurate with the correis readily adjustable to compensate for variations of sponding required cooling intensity increments 5 cooling requirements. across the web. 

2. A method according to claim 1, further characterized in that a. three fan jet streams are merged approximately at a point of intersection adjacent to the web surface.
 3. A method according to claim 2, further characterized in that a. the fan jet sprays extend transversely of the direction of movement of the web.
 4. A method according to claim 3, further characterized in that a. the jet fans produce cross-sectional projection patterns ranging from generally stripe-shaped to oblong oval shaped.
 5. A method according to claim 4, further characterized in that a. sprays of different fans are directed upon the surface of the web from different elevations thereabove.
 6. A method according to claim 5, further characterized in that a. the angles of the jet fans are adjusted in predetermined relation to each other and/or to the surface of the web to distribute coolant in suitably weighted quantities commensurate with the corresponding required cooling intensity increments across the web.
 7. A method according to claim 6, further characterized in that a. the quantitative output of the jets in individual fans is readily adjustable to compensate for variations of cooling requirements. 